Screenshots purport to show WhatsApp's new VoIP calling feature in action on Apple's iOS

Ubiquitous cross-platform messaging app WhatsApp's forthcoming Voice over IP calling functionality, set to roll out to users later this spring, appears to have been revealed early in a series of screenshots posted Friday.

The snaps detail an in-call screen sporting a design similar to iOS 7's default Phone app, with four circular buttons to mute the call, switch to a text messaging session, direct the call through the device's speaker, and hang up. The top of the display shows the contact's name, photo, and phone number, according to Italian Apple blog iPhoneItalia.

Calls made using the new feature will add a colored "call in progress" bar to the display when a user switches out of WhatsApp, similar to the method employed by other VoIP apps like Skype and Line to notify the user that a call is still live. That functionality is provided by iOS APIs, though developers can modify its color and labeling.

Additionally, the company has made it easier for users to attach photos to a text message, adding a small camera button at the top of the keyboard. That small but welcome tweak cuts down on what was previously a multi-step process.

WhatsApp — recently acquired by Facebook in a $19 billion deal — will reportedly not charge for the calling service as it seeks to reach feature parity with more established competitors. In addition to other messaging apps, it is also competing with built-in Apple services like iMessage, FaceTime, and the new FaceTime Audio VoIP offering.

WhatsApp has yet to reveal an exact release date, and it is also unclear if any other changes are in the works following the Facebook tie-up.

Additionally, the company has made it easier for users to attach photos to a text message, adding a small camera button at the top of the keyboard. That small but welcome tweak cuts down on what was previously a multi-step process.

It's still a multi-step process as you cannot add text to the picture you want to send. Besides, I use iOS by default, and only use WA if needed. Yet, one after the other, rich or poor, is moving over to an iPhone. I guess my 'world' is different than the 'world of FB' as they seem to think they'll have 3 million customers using WA.

Apple, iMessage on Android, PLEASE!!! As we know Android users will download it and then I can get to delete all my other crappy chat apps and use iMessage and its emoji set full-time. That would be a great way to improving my iPhone experience. Please, Apple, do it!

Have any other phone? Use Viber. Not as secure, but free and works most of the time. Users generally don't have privacy concerns with Viber.

Using WhatsApp? Deactivate you account if you don't want your private information to be sold to advertisers who then rape your e-mail inbox with junk messages.

Want a good cross-platform IM client? Use Telegram. Puts privacy first. Is new, so developer is going to put a lot of efforts in improving it. Is free. Has already gained a lot of users since the humongous WhatsApp buyout.

Apple, iMessage on Android, PLEASE!!! As we know Android users will download it and then I can get to delete all my other crappy chat apps and use iMessage and its emoji set full-time. That would be a great way to improving my iPhone experience. Please, Apple, do it!

I doubt iMessage will ever be cross platform. Very good reasons for it:

1. Apple would most probably not get into making it compatible with other platforms. It requires a lot of efforts, and Apple already have a lots of work of their own.

2. iMessage is one of the signature apps in the Apple ecosystem. It influences sales and promotes a single ecosystem-minded purchase.